brace-expansion: Zero-step sequence causes process hang and memory exhaustion

### Impact A brace pattern with a zero step value (e.g., `{1..2..0}`) causes the sequence generation loop to run indefinitely, making the process hang for seconds and allocate heaps of memory. The loop in question: https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184 `test()` is one of https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113 The increment is computed as `Math.abs(0) = 0`, so the loop variable never advances. On a test machine, the process hangs for about 3.5 seconds and allocates roughly 1.9 GB of memory before throwing a `RangeError`. Setting max to any value has no effect because the limit is only checked at the output combination step, not during sequence generation. This affects any application that passes untrusted strings to expand(), or by error sets a step value of `0`. That includes tools built on minimatch/glob that resolve patterns from CLI arguments or config files. The input needed is just 10 bytes. ### Patches Upgrade to versions - 5.0.5+ A step increment of 0 is now sanitized to 1, which matches bash behavior. ### Workarounds Sanitize strings passed to `expand()` to ensure a step value of `0` is not used.

Source published

26 Mar 2026 18:29:42 UTC

Source modified

10 Sep 2026 03:51:00 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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